SALT LAKE CITY (AP) - Environmental activists argue in a new lawsuit that the federal government needs to step in to control emissions from aging coal-fired power plants near three national parks in Utah.

Three groups say that state regulators have missed a deadline to make a plan for controlling thousands of pounds of haze-causing pollution emitted daily from the two plants located within 100 miles of Arches, Canyonlands and Capitol Reef national parks.

EPA officials told the Associated Press on Wednesday they’re working with Utah authorities to revise parts of a plan the federal agency rejected in 2012. State regulators say large parts of the plan are already done, and they plan to produce new rules as soon as June.

HEAL Utah Director Matt Pacenza said the plaintiffs want the U.S. Environmental Protection Agency to set a new, enforceable deadline for the emission-control plan.

“We’re sympathetic to the complicated processes that both the state of Utah and the EPA have to go through,” he told the Salt Lake Tribune (http://bit.ly/1CplA0v ). “But we also want to make sure they realize we need to get this done as soon as possible.”

A Rocky Mountain Power spokesman tells the AP that the two plants located in Emery County produce enough energy to power the equivalent of one million homes, and much of that power is used within Utah.

The environmentalists also take issue with proposed Utah regulations released in October that don’t require pollution-reducing retrofits that the power company said would be too expensive.

Rocky Mountain power spokesman Dave Eskelsen says the company has already installed emissions controls at the two plants built in the late 1970s and early 1980s, and more retrofitting could increase rates and wouldn’t help much.

Similar lawsuits have been filed in other states, and are designed to push the federal agency into action, said Cory MacNulty with the National Parks Conservation Association.

“Every year that is delayed is another year where visitors are being exposed to unhealthy air in the parks,” MacNulty told the Tribune.

Pacenza says the state needs the pollution controls to protect both the scenic national parks and people’s health.

“They’re not just bad for our views,” he said. “They’re bad for our communities and families.”

HEAL Utah joined the Sierra Club and the National Parks Conservation Association to file the federal suit last week in Denver. A hearing in the case is set for June 8.